Semiconductor structures and methods of forming the same

ABSTRACT

A semiconductor structure includes a dielectric layer disposed over a substrate. A metallic line is disposed in the dielectric layer. A through-silicon-via (TSV) structure continuously extends through the dielectric layer and the substrate. A surface of the metallic line is substantially leveled with a surface of the TSV structure.

TECHNICAL FIELD

The present disclosure relates generally to the field of semiconductor and, more particularly, to semiconductor structures and methods of forming the same.

BACKGROUND

Since the invention of the integrated circuit, the semiconductor industry has experienced continual rapid growth due to continuous improvements in the integration density of various electronic components (i.e., transistors, diodes, resistors, capacitors, etc.). For the most part, this improvement in integration density has come from repeated reductions in minimum feature size, allowing for the integration of more components into a given area.

These integration improvements are essentially two-dimensional (2D) in nature, in that the volume occupied by the integrated components is essentially on the surface of the semiconductor wafer. Although dramatic improvements in lithography have resulted in considerable improvements in 2D integrated circuit formation, there are physical limits to the density that can be achieved in two dimensions. One of these limits is the minimum size needed to make these components. Also, when more devices are put into one chip, more complex designs are required.

Three-dimensional integrated circuits (3D IC) are therefore created to resolve the above-discussed limitations. In a conventional formation process of 3D IC, two wafers, each including an integrated circuit, are formed. The wafers are then bonded with the devices aligned. Deep vias are then formed to interconnect devices on the first and second wafers.

Recently, through-silicon-vias (TSVs), also referred to as through-wafer vias, are increasingly used as a way of implementing 3D IC. Generally, a bottom wafer is bonded to a top wafer. Both wafers include integrated circuits formed over substrates. The integrated circuits in the bottom wafer are connected to the integrated circuits in the wafer through interconnect structures. The integrated circuits in the wafers are further connected to external pads through through-silicon-vias. The stacked wafers can be subjected to a sawing process to provide a plurality of stacked die structures.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale and are used for illustration purposes only. In fact, the numbers and dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1 is a schematic cross-sectional view of an exemplary semiconductor structure.

FIG. 2 is a schematic cross-sectional view of another exemplary semiconductor structure.

FIG. 3 is a flowchart of an exemplary method of forming a semiconductor structure including a TSV structure through a substrate.

FIGS. 4A-4K are schematic cross-sectional views of a semiconductor structure during various fabrication stages.

DETAILED DESCRIPTION OF THE DISCLOSURE

A method of forming a TSV structure that is known to the applicants includes forming an interlayer dielectric (ILD) layer over a substrate. A TSV opening is patterned through the ILD layer and into the substrate. An oxide liner and a TSV metallic material are sequentially deposited over the ILD layer and filled in the TSV opening. The oxide liner and the TSV metallic material is then subjected to a chemical mechanical polish (CMP) process, such that portions of the oxide liner and the TSV metallic material that are over the ILD layer are removed.

After the CMP process, an inter-metal dielectric 1 (IMD 1) layer is formed over the ILD layer and the TSV structure. Metallic lines or plugs of a metal 1 (M1) layer are then formed in the IMD 1 layer and electrically coupled with the TSV structure and contact plugs in the ILD layer. That is, an interface is between the TSV structure and the metallic plug formed thereon.

The width of the TSV opening may be increased due to the process/technology node evolution. Due to the wider TSV opening, a thicker oxide liner is deposited in the TSV opening. To remove the portion of the oxide liner over the ILD layer, the CMP process may also substantially remove the ILD layer and damage the contact plugs formed therein.

It is understood that the following disclosure provides many different embodiments, or examples, for implementing different features of the disclosure. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. Moreover, the formation of a feature on, connected to, and/or coupled to another feature in the present disclosure that follows may include embodiments in which the features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the features, such that the features may not be in direct contact. In addition, spatially relative terms, for example, “lower,” “upper,” “horizontal,” “vertical,” “above,” “below,” “up,” “down,” “top,” “bottom,” etc. as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) are used for ease of the present disclosure of one features relationship to another feature. The spatially relative terms are intended to cover different orientations of the device including the features.

FIG. 1 is a schematic cross-sectional view of an exemplary semiconductor structure. In FIG. 1, a semiconductor structure 100 includes a dielectric layer 110 that is disposed over a substrate 101. The semiconductor structure 100 includes a metallic line 120 that is disposed in the dielectric layer 110. A through-silicon-via (TSV) structure 130 that continuously extends through the dielectric layer 110 and the substrate 101. A surface 121 of the metallic line 120 is substantially level with a surface 131 of the TSV structure 130.

In some embodiments, the substrate 101 may include an elementary semiconductor including silicon or germanium in a crystalline, a polycrystalline, or an amorphous structure; a compound semiconductor including silicon carbide, gallium arsenide, gallium phosphide, indium phosphide, indium arsenide, and/or indium antimonide; an alloy semiconductor including SiGe, GaAsP, AlInAs, AlGaAs, GaInAs, GaInP, and/or GaInAsP; any other suitable material; or combinations thereof. In at least one embodiment, the alloy semiconductor substrate may have a gradient SiGe feature in which the Si and Ge composition change from one ratio at one location to another ratio at another location of the gradient SiGe feature. In another embodiment, the alloy SiGe is formed over a silicon substrate. In another embodiment, a SiGe substrate is strained. Furthermore, the semiconductor substrate may be a semiconductor on insulator, such as a silicon on insulator (SOI), or a thin film transistor (TFT). In some examples, the semiconductor substrate may include a doped epi layer or a buried layer. In other examples, the compound semiconductor substrate may have a multilayer structure, or the substrate may include a multilayer compound semiconductor structure.

In some embodiments, an isolation structure 105 is formed in the substrate 101 as shown in FIG. 1. The isolation structure 105 can be a shallow trench isolation (STI) structure, a local oxidation of silicon (LOCOS) structure, and/or any combinations thereof. The isolation structure 105 can be made of at least one material, such as silicon oxide, silicon nitride, silicon oxynitride, other dielectric materials, and/or any combinations thereof.

In some embodiments, the dielectric layer 110 can be made of at least one material, such as silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, silicon oxycarbide, silicon carbon nitride, a low dielectric constant (low-k) dielectric material, an ultra low-k dielectric material, and/or any combinations thereof. In some embodiments, a surface 111 of the dielectric layer 110 is substantially leveled with the surface 131 of the TSV structure 130.

Referring to FIG. 1, in some embodiments the dielectric layer 110 continuously extends between the TSV structure 130 and the substrate 101. For example, the dielectric layer 110 can include portions 110 a and 110 b. The portion 110 a can continuously extend between the substrate 101 and the TSV structure 130. The portion 110 b can extend over a surface 101 a of the substrate 101. In some embodiments, the portion 110 a has a thickness T₁ and the portion 110 b has a thickness T₂. The thickness T₁ is larger than the thickness T₂. In some embodiments, the dielectric layer 110 is referred to as a liner layer that continuously extends over the substrate 101 and on sidewalls of an opening (not labeled) in which the portion 110 a and the TSV structure 130 are disposed.

Referring to FIG. 1, the metallic line 120 is disposed over the substrate 101. The metallic line 120 can be routed for electrical connection. In some embodiments, the metallic line 120 can include at least one barrier material and at least one conductive material (not labeled). The at least one barrier material can include, for example, titanium, titanium-nitride, tantalum, tantalum-nitride, other barrier materials, and/or combinations thereof. The at least one conductive material can include, for example, aluminum, copper, aluminum-copper, polysilicon, other conductive materials, and/or combinations thereof.

Referring again to FIG. 1, the TSV structure 130 continuously extends through the substructure 101 and the dielectric layer 110. In some embodiments, the TSV structure 130 can include at least one barrier material and at least one conductive material (not labeled). The at least one barrier material can include, for example, titanium, titanium-nitride, tantalum, tantalum-nitride, other barrier materials, and/or combinations thereof. The at least one conductive material can include, for example, aluminum, copper, aluminum-copper, polysilicon, other conductive materials, and/or combinations thereof.

In some embodiments, the semiconductor structure 100 may include various passive and active microelectronic devices, such as resistors, capacitors, inductors, diodes, metal-oxide-semiconductor field effect transistors (MOSFETs), complementary MOS (CMOS) transistors, bipolar junction transistors (BJTs), laterally diffused MOS (LDMOS) transistors, high power MOS transistors, FinFET transistors, other types of transistors, and/or any combinations thereof.

For example, the semiconductor structure 100 includes at least one transistor, e.g., a transistor 140 that is disposed over the substrate 101 as shown in FIG. 1. The transistor 140 is electrically coupled with the metallic line 120 through at least one contact plug, e.g., a contact plug 145. The contact plug 145 is disposed in and through a dielectric layer 133 that is disposed over the substrate 101. In some embodiments, the TSV structure 130 does not have an interface at a region 132 that is substantially leveled with an interface between the contact plug 145 and the metallic line 120.

In some embodiments, the dielectric layer 133 can be made of at least one material, such as silicon oxide, e.g., undoped silicate glass (USG), boron-doped silicate glass (BSG), phosphor-doped silicate glass (PSG), boron-phosphor-doped silicate glass (BPSG), or the like, silicon oxy-nitride, silicon nitride, a low-k material, and/or any combinations thereof. In some embodiments, the dielectric layer 133 is referred to as an inter-layer dielectric (ILD) layer. It is noted that though merely showing a single dielectric layer 133 in FIG. 1, the scope of this application is not limited thereto. In some embodiments, a multiple-layer dielectric structure can be disposed over the substrate 101.

In some embodiments, at least one etch-stop layer, e.g., an etch-stop layer 135 is disposed between the dielectric layers 110 and 133. In some embodiments, the etch-stop layer 135 can be made of a material including at least one of, for example, nitride, oxynitride, carbide, oxycarbide, other dielectric materials having an etch selectivity substantially different from that of the dielectric layer 133, and/or any combinations thereof. It is noted that though merely showing a single etch-stop layer 135 in FIG. 1, the scope of this application is not limited thereto. In some embodiments, a multiple-layer etch-stop structure can be disposed over the dielectric layer 133 and the substrate 101.

Referring again to FIG. 1, the metallic line 120 is disposed over the dielectric layer 133. In some embodiments, the metallic line 120 can be referred to as a portion of a metal-1 (M₁) layer. The portion 110 b of the dielectric layer 110 can be referred to as an inter-metal dielectric 1 (IMD1) layer. It is noted that the structure shown in FIG. 1 is merely exemplary and the scope of this application is not limited thereto. In some embodiments, the metallic line 120 can be a portion of any one of metal layers, e.g., M₂, M₃, M₄, etc. For example, the metallic line 120 is a portion of a M₂ layer. In at least this embodiment, the surface of the M₂ layer can be substantially leveled with the surface of the TSV structure 130. The TSV structure 130 does not have an interface at a region that is substantially leveled with an interface between the IMD1 layer and a IMD2 layer (not shown) that is disposed over the IMD1 layer and in which the M₂ layer is formed.

FIG. 2 is a cross-sectional view of another exemplary semiconductor structure. Items of a semiconductor structure 200 in FIG. 2 that are the same or similar items of the semiconductor structure 100 in FIG. 1 are indicated by the same reference numerals, increased by 100. In FIG. 2, a semiconductor structure can be an interposer 200. The interposer 200 can be configured to provide an electrical connection in a 3-dimensional (3-D) package system.

In some embodiments, the interposer 200 can include at least one passive device, e.g., a capacitor, a resistor, and/or an inductor. In other embodiments, the interposer 200 can be substantially free from including any active device, e.g., metal-oxide-semiconductor (MOS) transistors, bipolar junction transistors (BJTs), complementary MOS (CMOS) transistors, etc. In still other embodiments, the interposer 200 does not include any active device and passive device. The interposer 200 can be merely configured for providing an electrical connection. In yet still other embodiments, the interposer 200 can be referred to as a passive interposer.

Referring to FIG. 2, the interposer 200 includes a dielectric layer 210 that is disposed over a substrate 201. The interposer 200 includes a metallic line 220 that is disposed in the dielectric layer 210. A through-silicon-via (TSV) structure 230 that continuously extends through the dielectric layer 210 and the substrate 201. A surface 221 of the metallic line 220 is substantially level with a surface 231 of the TSV structure 230. In some embodiments, a surface 211 of the dielectric layer 210 is substantially level with the surface 231 of the TSV structure 230.

In some embodiments, the dielectric layer 210 can include portions 210 a and 210 b. The portion 210 a can be disposed between the substrate 201 and the TSV structure 230. The portion 210 b can be disposed over the substrate 201. In some embodiments, the dielectric layer 210 can be referred to as a liner layer that continuously extends over the substrate 201 and on sidewalls of an opening (not labeled) in which the portion 210 a and the TSV structure 230 are disposed. In other embodiments, the portion 210 b of dielectric layer 210 can be referred to as a dielectric material portion of a redistribution layer (RDL). The metallic line 220 can be referred to as a conductive material portion of the RDL.

FIG. 3 is a flowchart of an exemplary method of forming a semiconductor structure including a TSV structure through a substrate. FIGS. 4A-4K are schematic cross-sectional views of a semiconductor structure during various fabrication stages. Items of a semiconductor structure 400 in FIGS. 4A-4K that are the same or similar items of the semiconductor structure 100 in FIG. 1 are indicated by the same reference numerals, increased by 300. It is understood that FIGS. 3 and 4A-4K have been simplified for a better understanding of the concepts of the present disclosure. Accordingly, it should be noted that additional processes may be provided before, during, and after the methods of FIGS. 3 and 4A-4K, and that some other processes may only be briefly described herein.

Referring to FIG. 3, a method 300 of forming a semiconductor structure includes forming a through-silicon-via (TSV) opening in a substrate (block 310). A dielectric layer is formed, continuously extending over the substrate and into the TSV opening (block 320). At least one conductive material is formed over the dielectric layer and in the TSV opening (block 330). A portion of the at least one conductive material that is over the dielectric layer is removed to form a TSV structure in the substrate (block 340). A metallic line is formed in the dielectric layer (block 350). A portion of the substrate is removed, such that the TSV structure continuously extends through the substrate and the dielectric layer (block 360).

In some embodiments, a semiconductor structure 400 includes a substrate 401 as shown in FIG. 4A. At least one isolation structure, e.g., an isolation structure 405 is formed in the substrate 401. At least one transistor, e.g., a transistor 440 is formed over the substrate 401. A dielectric layer 433 is formed over the substrate 401. At least one contact plug, e.g., a contact plug 445 is formed in the dielectric layer 433. An etch stop layer 435 is formed over the dielectric layer 433. In some embodiments, the dielectric layer 433 can have a thickness of about hundreds to thousands of angstroms (Å).

Referring again to FIG. 3, the block 310 includes forming a through-silicon-via (TSV) opening in a substrate. For example, a TSV opening 415 is formed in the substrate 401 as shown in FIG. 4B. In some embodiments, the TSV opening 415 is formed through the etch stop layer 435, the dielectric layer 433 and the isolation structure 405. In some embodiments, the TSV opening 415 has a dimension (D) of about several to tens of microns (μm).

In some embodiments, the TSV opening 415 can be patterned by forming a patterned mask layer (not shown) over the etch stop layer 435. The patterned mask layer exposes a region corresponding to the portions of the etch stop layer 435, the dielectric layer 433, the isolation structure 405 and the substrate 401 that are to be removed. An etching process, e.g., a dry etching process, by using the patterned mask layer as an etch mask, can remove the portions of the etch stop layer 435, the dielectric layer 433, the isolation structure 405 and the substrate 401 to form the TSV opening 415. After the etching processing, the patterned mask layer is removed.

As noted, the block 320 (shown in FIG. 3) includes forming a dielectric layer that continuously extends over a substrate and into the TSV opening. For example, a dielectric layer 408 is formed and continuously extends over the substrate 401 and into the TSV opening 415 as shown in FIG. 4C. In some embodiments, a portion of the dielectric layer 408 is formed over the etch stop layer 435 and the dielectric layer 433. In other embodiments, the dielectric layer 408 is substantially conformal over the etch stop layer 435 and in the TSV opening 415. The dielectric layer 408 can be formed by, for example, chemical vapor deposition (CVD), high density plasma CVD, and/or other suitable methods. In some embodiments, the dielectric layer 408 can be referred to as a liner layer. In other embodiments, the dielectric layer 408 can have a thickness T₁′ ranging from about thousands of angstroms to about several microns.

Referring to FIG. 3, the block 330 includes forming at least one conductive material over the dielectric layer and in the TSV opening. For example, at least one conductive material 428 is formed over the dielectric layer 408 and in the TSV opening 415 as shown in FIG. 4D. In some embodiments, the at least one conductive material 428 can include a barrier metallic material and a metallic material. In some embodiments, the barrier metallic material is substantially conformal in the TSV opening 415. The barrier metallic material can be formed by, for example, CVD, physical vapor deposition (PVD), atomic layer deposition (ALD), and/or other suitable processes. The metallic material can be formed by, for example, CVD, electroplating, and/or other suitable processes to fill the metallic material in the TSV opening 415.

Referring to FIG. 3, the block 340 includes removing a portion of the at least one conductive material that is over the dielectric layer to form a TSV structure in the substrate. For example, a removal process 409 removes a portion of the at least one conductive material 428 that is over the dielectric layer 408 to form a TSV structure 430 in the substrate 401 as shown in FIG. 4E. In some embodiments, the removal process 409 can include a chemical mechanical polish (CMP) process, a dry etching process, and/or any combinations thereof. The TSV structure 430 at this stage is not formed completely through the substrate 401.

In some embodiments, the removal process 409 may also remove a portion of the dielectric layer 408 that is adjacent to the at least one conductive material 428 (shown in FIG. 4D). The remaining portion of the dielectric layer 408 is referred to as a dielectric layer 408 a. In at least this embodiment, the thickness T₁′ of the dielectric layer 408 (shown in FIG. 4D) is reduced to the thickness T₂′ of the dielectric layer 408 a (shown in FIG. 4E).

Referring to FIG. 3, the block 350 includes forming a metallic line in the dielectric layer. In some embodiments, forming the metallic line can include forming a cap layer 437 over the dielectric layer 408 a as shown in FIG. 4F. The cap layer 437 can be made of at least one material that is similar to or the same as the material of the etch stop layer 435. The etch stop layer 435 can be provided to protect the TSV structure 430 from being oxidized and/or interacting with a patterned mask layer 439 that is formed thereon.

In some embodiments, the block 350 can include forming the patterned mask layer 439 over the cap layer 437. The patterned mask layer 439 has at least one opening, e.g., an opening 441 that exposes a portion of the cap layer 437 (not labeled). In FIG. 4F, the patterned mask layer 439 covers the TSV structure 430. In some embodiments, the patterned mask layer 439 can be made of a photoresist material.

In some embodiments, the block 350 can include an etching process removing the exposed portion of the cap layer 437 and a portion of the dielectric layer 408 a by using the patterned mask layer 439 as an etch mask to form an opening 442 in the dielectric layer 408 a as shown in FIG. 4G. In some embodiments, the etching process can also remove a portion of the etch stop layer 435 to expose a top surface of the contact plug 445.

In some embodiments, the block 350 can include a removal process removing the patterned mask layer 439 as shown in FIG. 4H. The removal process can include a photoresist removal process. As shown in FIG. 4H, the opening 442 is patterned in the cap layer 437, the dielectric layer 408 a and the etch stop layer 435.

In some embodiments, the block 350 can include forming the metallic line in the opening 422 in the dielectric layer 408 a. For example, the block 350 can include forming at least one metallic material 418 over the cap layer 437 and in the opening 422 as shown in FIG. 4I. In some embodiments, the at least one metallic material 418 can include a barrier metallic material and a metallic material. The barrier metallic material can be formed by, for example, CVD, physical vapor deposition (PVD), atomic layer deposition (ALD), and/or other suitable processes. The metallic material can be formed by, for example, CVD, electroplating, and/or other suitable processes to fill the metallic material in the opening 422.

In some embodiments, the block 350 can include removing a portion of the at least one metallic material 418 that is over the dielectric layer 408 a by a chemical mechanical polish (CMP) process 449 to form the metallic line 420 in the opening 422, wherein a surface 431 of the TSV structure 430 is substantially leveled with a surface 421 of the metallic line 420 as shown in FIG. 4J. In some embodiments, the surface 431 of the TSV structure 430 is substantially leveled with a surface 411 of the dielectric layer 408 a.

Referring again to FIG. 3, the block 360 includes removing portions of the substrate and the dielectric layer. For example, bottom portions of the substrate 401 and the dielectric layer 408 a are removed such that the dielectric layer 410 is formed over the substrate 401 and around the TSV structure 430 as shown in FIG. 4K. By removing the bottom portions of the substrate 401 and the dielectric layer 408 a, the TSV structure 430 is formed, continuously extending through the substrate 401 and the dielectric layer 410.

As shown in FIG. 4K, the dielectric layer 410 can include portions 410 a and 410 b. The portion 410 a can be disposed between the substrate 401 and the TSV structure 430. The portion 410 b can be disposed over the substrate 401. In some embodiments, the portion 410 a is thicker than the portion 410 b.

As noted, the dielectric layer 408 is formed as a liner layer continuously extending over the substrate and along the sidewalls of the TSV opening 415 as shown in FIG. 4C. The portion of the dielectric layer 408 that is over the etch stop layer 435 is used as a IMD layer in which the metallic line 420 is formed.

In a first exemplary embodiment, a semiconductor structure includes a dielectric layer disposed over a substrate. A metallic line is disposed in the dielectric layer. A through-silicon-via (TSV) structure continuously extends through the dielectric layer and the substrate. A surface of the metallic line is substantially leveled with a surface of the TSV structure.

In a second exemplary embodiment, a method of forming a semiconductor structure includes forming a through-silicon-via (TSV) opening in a substrate. A dielectric layer is formed, continuously extending over the substrate and into the TSV opening. At least one conductive material is formed over the dielectric layer and in the TSV opening. A portion of the at least one conductive material that is over the dielectric layer is removed to form a TSV structure in the substrate. A metallic line is formed in the dielectric layer. A portion of the substrate is removed, such that the TSV structure continuously extends through the substrate and the dielectric layer.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. 

1. A semiconductor structure comprising: a dielectric layer disposed over a substrate; a metallic line disposed in the dielectric layer; and a through-silicon-via (TSV) structure continuously extending through the dielectric layer and the substrate, wherein a surface of the metallic line is substantially level with a surface of the TSV structure.
 2. The semiconductor structure of claim 1, wherein a surface of the dielectric layer is substantially level with the surface of the TSV structure.
 3. The semiconductor structure of claim 1, further comprising: at least one contact plug that is electrically coupled between the metallic line and a transistor that is disposed over the substrate.
 4. The semiconductor structure of claim 3, wherein the TSV structure is continuous at a region that is substantially level with an interface between the at least one contact plug and the metallic line.
 5. The semiconductor structure of claim 1, wherein the dielectric layer continuously extends between the TSV structure and the substrate.
 6. The semiconductor structure of claim 5, wherein a first portion of the dielectric layer that is between the TSV structure and the substrate is thicker than a second portion of the dielectric layer that is over the substrate.
 7. The semiconductor structure of claim 1, wherein the semiconductor structure is an interposer and the metallic line is a portion of a redistribution layer (RDL) of the interposer.
 8. A semiconductor structure comprising: a through-silicon-via (TSV) structure continuously extending through a substrate; a liner layer continuously extending over the substrate and between the TSV structure and the substrate, wherein a surface of the liner layer is substantially level with a surface of the TSV structure; and a metallic line disposed in the liner layer.
 9. The semiconductor structure of claim 8, wherein a surface of the metallic line is substantially level with the surface of the TSV structure.
 10. The semiconductor structure of claim 8, further comprising: at least one contact plug that is electrically coupled between the metallic line and a transistor that is disposed over the substrate.
 11. The semiconductor structure of claim 10, wherein the TSV structure is continuous at a region that is substantially level with an interface between the at least one contact plug and the metallic line.
 12. The semiconductor structure of claim 8, wherein a first portion of the liner layer that is between the TSV structure and the substrate is thicker than a second portion of the liner layer that is over the substrate.
 13. The semiconductor structure of claim 8, wherein the semiconductor structure is an interposer and the metallic line is a portion of a redistribution layer (RDL) of the interposer.
 14. A method of forming a semiconductor structure, the method comprising: forming a through-silicon-via (TSV) opening in a substrate; forming a dielectric layer continuously extending over the substrate and into the TSV opening; forming at least one conductive material over the dielectric layer and in the TSV opening; removing a portion of the at least one conductive material that is over the dielectric layer to form a TSV structure in the substrate; forming a metallic line in the dielectric layer; and removing a portion of the substrate, such that the TSV structure continuously extends through the substrate and the dielectric layer.
 15. The method of claim 14, wherein forming the metallic line comprises: forming a cap layer over the dielectric layer; forming a patterned mask layer over the cap layer, the patterned mask layer covering the TSV structure and exposing a portion of the cap layer; removing the exposed portion of the cap layer and a portion of the dielectric layer by using the patterned mask layer as an etch mask to form an opening in the dielectric layer; removing the patterned mask layer; and forming the metallic line in the opening in the dielectric layer.
 16. The method of claim 15, wherein forming the metallic line in the opening in the dielectric layer comprises forming at least one metallic material over the cap layer and in the opening in the dielectric layer; and removing a portion of the at least one metallic material that is over the dielectric layer by a chemical mechanical polish (CMP) process to form the metallic line in the opening in the dielectric layer, wherein a surface of the TSV structure is substantially leveled with a surface of the metallic line.
 17. The method of claim 15, wherein the cap layer is provided to protect the TSV structure from being oxidized by the patterned mask layer.
 18. The method of claim 14, further comprising: forming at least one transistor over the substrate; and forming at least one contact plug that is electrically coupled between the metallic line and the at least one transistor, wherein a surface of the dielectric layer is substantially leveled with the surface of the TSV structure.
 19. The method of claim 18, wherein the TSV structure does not have an interface at a region that is substantially leveled with an interface between the at least one contact plug and the metallic line. 